In recent years, an organic EL element that can achieves high-brightness emission by means of low-voltage DC drive has attracted attention as an emitting element that is used for a liquid crystal display and an electroluminescence (EL) display. It has been studied to use a transparent plastic film as an electrode substrate that is used for these displays in order to implement a reduction in thickness, a reduction in weight, an increase in flexibility, and the like.
An organic EL element deteriorates in emission properties (e.g., emission brightness, emission efficiency, and emission uniformity) when driven for a certain period of time. It is considered that such a problem occurs since the electrode, the organic layer (emitting layer), and the like included in the organic EL element deteriorate with the passing of time due to water vapor that has entered the organic EL element, and a non-emitting area occurs, for example. Various types of organic EL element sealing technology have been proposed to prevent the entry of water vapor into the organic EL element.
For example, Patent Literature 1 and 2 disclose a sealing method that uses a flexible film for an organic EL element.
According to the methods disclosed in Patent Literature 1 and 2, however, it is difficult to sufficiently suppress the entry of water vapor into the organic EL element, prevent deterioration in the organic EL element, and reliably and easily seal the organic EL element.
Therefore, development of a sealing sheet that exhibits an excellent gas (e.g., water vapor) barrier capability has been strongly desired.